The present invention relates to a yarn relaxation-heating method and an apparatus therefor. More particularly, the present invention relates to a yarn relaxation-heating method and a yarn relaxation-heating apparatus for use in false-twisting thermoplastic synthetic fiber such as polyester fiber, polyamide fiber, etc.
Heretofore, in false-twisting or rolling and false-twisting of such synthetic fiber, a so-called first heater which is a heating apparatus for false-twisting and fixation, and a so-called second heater which is a heating apparatus for performing relaxation-heating of yarn to improve thermal size stability to obtain low-stretchable false-twisted yarn are used as disclosed in JP-A-5-98530, JP-A-6-322625, JP-A-7-34338, JP-A-8-120533 or JP-A-10-331040.
In the second heater, heretofore, a non-contact grooved heater or a pipe heater is provided between a yarn supply roller (feed roller) and a take-up roller having a speed lower than that of the supply roller in order to perform relaxation-heating (contractive heating).
In a relaxation-heating apparatus using the background-art second heater, the temperature of the contact type pipe heater is limited to 230xc2x0 C. at the maximum. Moreover, it is necessary to make the pipe heater long for high-speed treatment. Hence, there is a problem that contact resistance becomes high. On the other hand, the high-temperature non-contact type grooved heater is poor in heat conductivity because the heater is of the non-contact type. Hence, the heater becomes long. Further, the temperature of a heating plate cannot but be made high. Moreover, there are various problems that heating spots are caused by swinging of yarn running at a high speed or caused by distortion of the yarn by the torque.
The present invention is designed in consideration of such problems and provides a relaxation-heating method and an apparatus therefor, in which the size is compact, the heat conductivity is high, and yarn can be made to run at a high speed.
Incidentally, JP-U-60-9979 discloses a rolling and heating apparatus having a heating roller and a separate roller opposite to the heating roller. The heating roller has a roller diameter which is increased linearly in a longitudinal direction from the yarn input side toward the yarn output side, and has a temperature gradient so that the surface temperature of the roller is increased from the yarn input side toward the yarn output side. Further, U.S. Pat. No. 3,803,674 discloses a method and an apparatus for heating thermoplastic yarn. The apparatus has, for example, two rollers (68, 69) separated from each other.
As means for solving the aforementioned problem, the method according to the present invention has a feature in which relaxation-heating is performed by a heating apparatus which is provided between a yarn supply roller and a take-up roller having a speed lower than that of the supply roller, the heating apparatus being constituted by a heating roller and an auxiliary bobbin.
Further, the apparatus according to the present invention is has a feature in that the apparatus is provided with a yarn supply roller, a take-up roller having a speed lower than that of the supply roller, and a heating apparatus provided between the take-up roller and the supply roller and constituted by a heating roller and an auxiliary bobbin. As a result, the apparatus is compact in size and high in heat conductivity. Further, the apparatus can prevent occurrence of various heating spots which are generated by the running of yarn. Other features, operations and effects of the present invention will be described in detail in the following disclosure.